I collect all the new calendars for iOS, even the terribly strange ones (for example, try to use–or to even pronounce–“Schelandars“).
One of my favorites is currently iCalendar which has a nice clean display and a simple interface for linking contacts and places to an event.
Of course any of these iOS calendars can show events from FileMaker if you’re using SeedCode Subscribe: once you add a Subscribe URL as a source on your iPhone it’s available to any calendar app on your phone. (SeedCode Subscribe requires FileMaker Server.)
Fantastical is probably still the reigning iOS calendar (and I use their desktop calendar to show FileMaker events as well) but iCalendar is definitely worth checking out.